London, May 9 (ANI): Sex beast Josef Fritzl humiliated his dowdy wife at a swingers club by forcing her to watch him romp with another woman.

Paul Stocker, a builder - who tried to sell Fritzl a house - claims he saw him at the Caribik Club, near Amstetten, back in 1997.

"An elderly couple came in, they looked just like an old pair you might see in a park feeding the pigeons," the Mirror quoted Stocker, as saying.

"I was speechless when I realised it was Fritzl with his wife. She went without a word to stand in the corner.

"He treated her like a dog. She had to sit in a corner and watch as he did stuff with a young woman."

Stocker also told how Fritzl bragged about using Viagra to boost his sex life. (ANI)